Fuel injection pump for internal combustion engines and method of fuel control

ABSTRACT

In a fuel injection pump, in order to prolong the duration of fuel injection during each pressure stroke of the pump piston in the idling or low load rpm range, there is provided a bypass channel extending from the pump work chamber for continuously discharging part of the fuel displaced by the pump piston. Said bypass channel contains a valve means which closes the bypass channel when the engine rpm exceeds the idling or low load rpm range.

United States Patent Eckert et al. 5] Oct. 24, 1972 [S4] FUEL INJECTIONPUMP FOR {56] References Cited INTERNAL COMBUSTION ENGINES UNITED STATESPATENTS AND METHOD OF FUEL CONTROL 3,403,629 10/ l 968 Eheim et al..4l7/293 2] Inventors: Konrad Eckert, Stuttgart-Bad Carm- 3,417,70312/1968 Eckert et a]. ..417/293 tan; Flalll m; Gerald Holer, 3,456,6297/1969 Dangauthier 123/139 AS both of Stuttgart; Claus Koster, 3,332,4087/1967 Scott et a] ..123/ 140 A Ditzingen, all of Germany 2,173,8149/1939 Bischoi' ..123/l39 R Assignw Robert Bosch 8mm 1222232 31333$3321.??? 'Yifii/SX 2,449,382 9/1948 Huber ..123/139 AS [22] Filed: June8, 1970 Primary Examiner-laurence M. Goodridge Assistant ExaminerCortFlint [2]] Appl' 444,17 Attorney-Edwin E. Greigg [30] ForeignApplication Priority Data [57] ABSTRACT in a fuel injection pump, inorder to prolong the duration of fuel injection during each pressurestroke of June 19,1969 Germany ..P 19 31039.5 the pump piston in theidling or low load rpm range, there is provided a bypass channelextending from the [52] Cl "123,140 7/293 l pump work chamber forcontinuously discharging part 1 of the fuel displaced by the pumppiston. Said bypass channel contains a valve means which closes the [51]int. Cl ..F02d 1/04 bypass channel when the engine rpm exceeds the 58Field of Search 123/1401, 140 A, 140 F0, dlmg bad 123/140 AS, 139 AM,140; 417/293 10 Claims, 3 Drawing Figures PATENTEDUBT 24 I972 INVENTOR.Konrad ECKERT, Franz EHE/M Gerald HOFER,C/au

FUEL INJECTION PUMP FOR INTERNAL COMBUSTION ENGINES AND METHOD OF FUELCONTROL BACKGROUND OF THE INVENTION This invention relates to a fuelinjection pump for internal combustion engines and is of the type whichis provided with at least one reciprocating pump piston and with bypasschannel means extending from the pump work chamber and including athrottle.

When Diesel engines operate in the lower rpm range, the combustionnoises are very substantial, particularly during idling and under lowload conditions. Besides thermal effects, the reason therefor is therelatively short duration of injection, corresponding to the small fuelquantities to be injected in this range of engine operation. Byprolonging the duration of injection, for example, by extending theeffective duration of fuel delivery during each delivery stroke of thefuel injection pump, the combustion noise may be substantiallydecreased.

An aforenoted prolongation of the injection period is obtained by meansof the so-called advance injection methods in which first a small fuelquantity is injected followed by the main fuel quantity. In a known fuelinjection pump of the aforenoted type (such as disclosed in French Pat.No. 1,495,537), for practicing such an advance injection, the bypasschannel leads into a hydraulic accumulator, the pressure characteristicsof which are variable for altering the course of the injection. Such anarrangement, however, is complex and disadvantageous for high partialload or full load conditions since, even when the accumulator piston isblocked in this rpm range, the structurally necessary enlargement of thedetrimental space of the pump work chamber has an adverse effect on thecourse of the injection.

OBJECT AND SUMMARY OF THE INVENTION It is an object of the invention toprovide an improved fuel injection pump and method of the aforenotedtype wherein a prolongation of the injection period in the idling andlow load rpm range may be achieved by simple means with the eliminationof the aforenoted disadvantages.

Briefly stated, according to the invention, the bypass channel is closedbeyond the idling rpm by means of a valve which preferably is actuatedin unison with the fuel quantity control member of the fuel injectionpump.

The invention will be better understood as well as further objects andadvantages of the invention will become more apparent from the ensuingdetailed specification of a preferred, although exemplary embodiment,taken in conjunction with the drawing.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is an axial sectional view of afuel injection pump according to the preferred embodiment;

FIG. 2 is a view of one part shown in FIG. 1 after a 90 turn and FIG. 3is a diagram illustrating the function of the flow passage sections Fwith respect to the angle of rotation at of the fuel quantity control orsetting member.

DESCRIPTION OF THE PREFERRED EMBODIMENT Turning now to FIG. 1, the fuelinjection pump shown therein comprises a piston l which reciprocates ina cylinder 2, the upper portion of which, together with the radialterminal face of piston 1, defines a pump work chamber 3. The pumppiston l, which also serves as a distributor, sequentially supplies withfuel the cylinders (not shown) of a multi-cylinder internal combustionenginetalso not shown). The pump piston I is reciprocated andsimultaneously rotated as indicated by arrows A by means not shown.During each suction stroke of the piston l, the pump work chamber 3 issupplied with fuel from a suction chamber 4 through a control bore 5,one of the longitudinal grooves 6, an annular groove 7, and an axialbore 8 directly communicating with the pump work chamber 3. The axialbore 8 is provided in piston 1 and is connected with the annular groove7 by means of a transversal bore 9.

The pump piston l delivers fuel through a longitudinal distributorgroove 10 and through one of pressure channels 11, each of whichcontains a check valve 12. Each pressure channel 11 extends from thecylinder 2 and is connected with associated pressure conduits, notshown, which, in turn, extend to the individual fuel injection valves(also not shown), mounted in the internal combustion engine. Thelongitudinal distributor groove 10, the annular groove 7, as well as thelongitudinal grooves 6 are provided in the lateral face of the piston 1.The longitudinal distributor groove 10 terminates on the radial face ofthe piston 3 and thus merges into the pump work chamber 3. Thelongitudinal grooves 6, of which only two are shown in the drawing, andthe pressure or delivery channels 11, of which only one is shown, arearranged uniformly spaced about the circumference of piston l andcylinder 2 and their number equals that of the cylinders of the enginewith which the fuel injection pump is associated.

The fuel quantity control of the fuel injection pump is effected bymeans of a regulator shuttle 14 which is disposed between a bypasschannel portion 15a merging into the pump work chamber 3 and a bypasschannel portion 15b communicating with the suction chamber 4. Theregulator shuttle 14 controls the hydraulic communication between thebypass channel portions 15a and 15b. When such communication isestablished, the delivery of fuel to the engine is interrupted althoughthe pressure stroke of the pump piston is still in progress.

To control the afore-defined hydraulic communication by means of theregulator shuttle 14, the bypass channel portions 15a and 15b open intoa cylinder 16 in which the regulator shuttle l4 reciprocates. The latteris provided with an annular groove 17 which is in continuouscommunication with the bypass channel portion 15a, but, as shown in FIG.1, is separated from the bypass channel portion 15b when the regulatorshuttle I4 is in its position of rest determined by an abuttingrelationship between the pump housing and a flange 23 forming part ofthe regulator shuttle 14.

An enlarged portion of the piston I forms an auxiliary piston 18operating in a cylinder 19. The liquid displaced by the piston 18 shiftsthe regulator shuttle 14 in a direction of its forward motion. At thefrontal face of the piston 18 there terminate longitudinal grooves 20which are disposed on the lateral face of the piston 18 and which equalthe number of the longitudinal grooves 6. During the suction stroke ofthe auxiliary pump l8, 19, fuel is admitted from the suction chamber 4through a control bore 21 and longitudinal grooves 20 into the workchamber of the auxiliary pump 18, 19. During its pressure stroke, theauxiliary piston 18 forces fuel substantially through the channel 22into the cylinder 16 to affect the adjacent radial face of the regulatorshuttle l4.

The regulator shuttle 14, when displaced from its position of rest bythe fuel forced into cylinder 16 by the piston 18, shortly before theend of its possible path of travel, establishes communication betweenthe bypass channel portions a and 15b. At least one part of the fuelthat caused the forward motion of the regulator shuttle 14, is forced bythe latter, during its return motion caused by spring 24, through achannel 25 back into the cylinder 19 of the auxiliary pump. During thisoccurrence the channel 22 is closed by a check valve 26.

The channel 25 passes radially through a cylinder bore 27 in which thereis disposed a setting member 28 which is axially reciprocable androtatable as indicated by arrows B. in the lateral face of the latterthere is provided a circumferential control groove 29 which has anoblique control edge 36 to vary, during angular displacement of thesetting member 28, the flow passage section of a throttle 30 of thechannel 25. The diametrically opposite continuation of the channel 25freely merges into the control groove 29. Dependent upon the magnitudeof the flow passage section of throttle 30, the return motion of theregulator shuttle 14 is braked to a greater or lesser extent.

Beyond an rpm determined by the flow passage sec tion of the throttle30, the auxiliary pump l8, l9 begins a new pressure stroke before theregulator shuttle I4 is able to return to its initial position in whichflange 23 abuts the pump housing. By virtue of the so-called fluidabutment which appears under these conditions, the regulator shuttle l4begins its forward motion from an advanced initial position. As aresult, the bypass channel portions 150 and 15b are interconnected withone another at an earlier moment during the pressure stroke. in thismanner, the injected fuel quantities are decreased and, consequently,the rpm of the internal combustion engine, with which the fuel injectionpump is associated, also decreases.

A release bore 31 connects the cylinder 16 of the regulator shuttle 14with the suction chamber 4 and is closed by the lateral face of theregulator shuttle 14 during normal operation. The release bore 31, as asafety means, determines the extreme position which the regulatorshuttle 14 may assume during its forward motion subsequent tohydraulically connecting the bypass channels 15a, 15b with one another.

From the pump work chamber 3 there extends a bypass channel 34 to thesuction chamber 4. The channel 34 passes radially through cylinder 27and is controlled by the setting member 28. For this purpose, thesetting member 28 is provided with a longitudinal groove 35 which has abounding edge 38 extending parallel to the axis of the setting member 28and determines, dependent on the angular position of the setting member28, a flow passage section of throttle 37 of the channel 34 (FIG. 2).When the setting member 28 is rotated, the edge 38 of the groove 35passes over the discharge channel 34 and closes the latter. The controledge 38 is so arranged with respect to the oblique control edge 36 ofthe groove 29 of the setting member 28 that the bypass channel 34 isclosed at the moment when the rpm of the engine exceeds the low load rpmrange. By virtue of an axial displacement of the setting member 28effected by means of an adjusting screw not shown, this mechanism may bepre-set. In FIG. 2 a second, adjusted axial position of the settingmember 28 is shown in broken lines.

it is thus seen that in the low rpm ranges the fuel displaced by thepiston 1 while the bypass channel 15a, 15b is closed, is divided intotwo simultaneous flows: the first flow is injected into the enginethrough one of the pressure channels 11, while the second flow passesthrough the bypass channel 34 and is returned to the suction chamber 4.in this manner the duration of the injection of fuel during eachpressure stroke of piston l is prolonged because it takes longer todeliver the required fuel quantity by a partial fuel stream (i.e. by theaforedescribed second flow) than by a single flow. This effect iseliminated by closing the throttle 37 of the bypass channel 34 when theengine rpm exceeds the low rpm range.

in order to better adapt to the engine characteristics the fueldischarged through the bypass channel 34, there is provided a secondthrottle 39 associated with the bypass channel 34. The flow passagesection of the throttle 39 is variable by means of a setting screw 40.Also for the flow control, there is provided a check valve 41 disposedin the bypass channel 34 and having a closing spring, the force of whichmay be varied by means of an adjusting mechanism 42.

Turning now to the diagram shown in FIG. 3, the ordinate indicates thefree flow passage section F of the throttle 30, while the abscissaindicates the angle of rotation a of the setting member 28. The curves30' and 30" characterize the function of the flow passage section ofthrottle 30 in two different axial positions of setting member 28. Thecurve 37' relates to the flow passage section of the throttle 37. As itis seen from the diagram, when the setting member 28 is rotated in thedirection a, the throttle 30 is widened and the throttle 37 is sharplynarrowed. The throttle 37 is closed when the setting member 28 is turnedthrough an angle 01,. Thus, when the setting member 28 is rotated beyondthe angle 01,, the engine operates over the low load rpm range in whichthe bypass channel 34 is closed.

it is to be understood that the valve means controlling the bypasschannel 34 may be actuated electromagnetically or by hydraulic pressurethat increases with increasing rpm, or by other suitable means.

What is claimed is:

1. ln a fuel injection pump for an internal combustion engine, said pumpbeing of the type that includes a pump work chamber and at least onereciprocating pump piston associated with said chamber, the improvementcomprising,

A. a bypass channel extending from said pump work chamber to a space inwhich there prevails a pres sure that is lower than the pressure in saidpump work chamber at any time during each delivery stroke of saidreciprocating pump piston,

B. movable valve means disposed in said bypass channel to assume an openposition for maintaining communication between said pump work chamberand said space through said bypass channel and to assume a closedposition for blocking said bypass channel. said movable valve meansbeing in continuous communication with said pump work chamber throughsaid bypass channel at least for the entire duration of each deliverystroke and being in said open position for said entire duration at theidling rpm and C. means for moving said valve means into and maintainingit in said closed position when said engine operates over the idlingrpm.

2. An improvement as defined in claim 1, including a check valvedisposed in said bypass channel.

3. An improvement as defined in claim 1, including a fuel quantitysetting member and means to move said valve means together with saidsetting member as a rigid unit.

4. An improvement as defined in claim 3, wherein said movable valvemeans forms part of a variable throttle in said bypass channel to varythe flow passage section thereof between said open and said closedpositions of said movable valve means, said movable valve means and saidfuel quantity setting member form a unitary structure.

5. An improvement as defined in claim 4 including A. hydraulicallyoperated means for determining the injected fuel quantities byinterrupting the injection of fuel during one part of each deliverystroke of said reciprocating pump piston,

B. a channel communicating with said pressure-dependent means andcarrying hydraulic liquid and C. an additional variable throttle formingpart of said fuel quantity setting member and disposed in the lastnamedchannel for varying the flow passage section thereof to control saidhydraulically operated means.

6. An improvement as defined in claim 5, wherein said setting member isrotatably and axially displaceably held in said fuel injection pump;said additional throttle is variable by rotating and axially displacingsaid setting member; said bypass channel is closable by said settingmember upon rotation thereof.

7. An improvement as defined in claim 1, wherein said movable valvemeans forms part of a variable throttle in said bypass channel to varythe flow passage section thereof between said open and said closedpositions of said movable valve means.

8. An improvement as defined in claim 7, including an additionalthrottle disposed in said bypass channel remote from said movable valvemeans and means for arbitrarily varying said last-named throttleindependently from the first-named throttle.

9. In a fuel injection pump for an internal combustion engine, said pumpbeing of the type that includes a pump work chamber and at least onereciprocating main pump piston associated with said chamber, theimprovement comprising in combination,

A. a first bypass channel extending from said pump work chamber,

B. valve means disposed in said first bypass channel and continuouslycommunicating with said pump work chamber through said first bypasschannel at least for the entire duration of each delivery stroke of saidreciprocating main pump piston, said valve means being in an openposition for said entire duration at the idling rpm,

C. means actuating said valve means to close and maintain closed saidfirst bypass channel when said engine operates over the idling rpm,

D. a second bypass channel extending from said pump work chamber,

E. a regulator shuttle reciprocably disposed in said pump for openingand closing said second bypass channel,

F. return means urging said regulator shuttle into an initial positionof rest,

G. an auxiliary piston operating synchronously with said main pumppiston,

H. a first hydraulic channel establishing communication between saidauxiliary piston and said regulator shuttle,

l. a hydraulic liquid driven by said auxiliary pump during the pressurestrokes thereof through said first hydraulic channel to exert an enginerpm-dependent force on said regulator shuttle for displacing the latterin a forward motion from its initial position of rest to open saidsecond bypass channel thus interrupting fuel delivery to said engine bysaid main pump piston during the pressure strokes thereof,

J. a second hydraulic channel extending from said regulator shuttle;said regulator shuttle, displaced by said return means during thesuction strokes of said auxiliary piston, forces at least part of theliquid that caused its forward motion, through said second hydraulicchannel and K. a variable throttle disposed in said second hydraulicchannel to brake to a predetermined extent the return motion of saidregulator shuttle; upon reaching of a predetermined rpm at a givensetting of said throttle, said regulator shuttle reciprocates withoutreturning into said initial position of rest.

10. A method of prolonging the period of fuel injection into an internalcombustion engine during the idling rpm range by means of a fuelinjection pump of the type that includes a pump work chamber and atleast one reciprocating pump piston associated with said chamber,comprising the following steps:

A. discharging in said rpm range through a bypass channel extending fromsaid pump work chamber one part of the fuel displaced by said pumppiston throughout its pressure strokes and B. closing said bypasschannel by valve means when said engine operates beyond said rpm range.

i i i I l

1. In a fuel injection pump for an internal combustion engine, said pumpbeing of the type that includes a pump work chamber and at least onereciprocating pump piston associated with said chamber, the improvementcomprising, A. a bypass channel extending from said pump work chamber toa space in which there prevails a pressure that is lower than thepressure in said pump work chamber at any time during each deliverystroke of said reciprocating pump piston, B. movable valve meansdisposed in said bypass channel to assume an open position formaintaining communication between said pump work chamber and said spacethrough said bypass channel and to assume a closed position for blockingsaid bypass channel, said movable valve means being in continuouscommunication with said pump work chamber through said bypass channel atleast for the entire duration of each delivery stroke and being in saidopen position for said entire duration at the idling rpm and C. meansfor moving said valve means into and maintaining it in said closedposition when said engine operates over the idling rpm.
 2. Animprovement as defined in claim 1, including a check valve disposed insaid bypass channel.
 3. An improvement as defined in claim 1, includinga fuel quantity setting member and means to move said valve meanstogether with said setting member as a rigid unit.
 4. An improvement asdefined in claim 3, wherein said movable valve means forms part of avariable throttle in said bypass channel to vary the flow passagesection thereof between said open and said closed positions of saidmovable valve means, said movable valve means and said fuel quantitysetting member form a unitary structure.
 5. An improvement as defined inclaim 4 including A. hydraulically operated means for determining theinjected fuel quantities by interrupting the injection of fuel duringone part of each delivery stroke of said reciprocating pump piston, B. achannel communicating with said pressure-dependEnt means and carryinghydraulic liquid and C. an additional variable throttle forming part ofsaid fuel quantity setting member and disposed in the lastnamed channelfor varying the flow passage section thereof to control saidhydraulically operated means.
 6. An improvement as defined in claim 5,wherein said setting member is rotatably and axially displaceably heldin said fuel injection pump; said additional throttle is variable byrotating and axially displacing said setting member; said bypass channelis closable by said setting member upon rotation thereof.
 7. Animprovement as defined in claim 1, wherein said movable valve meansforms part of a variable throttle in said bypass channel to vary theflow passage section thereof between said open and said closed positionsof said movable valve means.
 8. An improvement as defined in claim 7,including an additional throttle disposed in said bypass channel remotefrom said movable valve means and means for arbitrarily varying saidlast-named throttle independently from the first-named throttle.
 9. In afuel injection pump for an internal combustion engine, said pump beingof the type that includes a pump work chamber and at least onereciprocating main pump piston associated with said chamber, theimprovement comprising in combination, A. a first bypass channelextending from said pump work chamber, B. valve means disposed in saidfirst bypass channel and continuously communicating with said pump workchamber through said first bypass channel at least for the entireduration of each delivery stroke of said reciprocating main pump piston,said valve means being in an open position for said entire duration atthe idling rpm, C. means actuating said valve means to close andmaintain closed said first bypass channel when said engine operates overthe idling rpm, D. a second bypass channel extending from said pump workchamber, E. a regulator shuttle reciprocably disposed in said pump foropening and closing said second bypass channel, F. return means urgingsaid regulator shuttle into an initial position of rest, G. an auxiliarypiston operating synchronously with said main pump piston, H. a firsthydraulic channel establishing communication between said auxiliarypiston and said regulator shuttle, I. a hydraulic liquid driven by saidauxiliary pump during the pressure strokes thereof through said firsthydraulic channel to exert an engine rpm-dependent force on saidregulator shuttle for displacing the latter in a forward motion from itsinitial position of rest to open said second bypass channel thusinterrupting fuel delivery to said engine by said main pump pistonduring the pressure strokes thereof, J. a second hydraulic channelextending from said regulator shuttle; said regulator shuttle, displacedby said return means during the suction strokes of said auxiliarypiston, forces at least part of the liquid that caused its forwardmotion, through said second hydraulic channel and K. a variable throttledisposed in said second hydraulic channel to brake to a predeterminedextent the return motion of said regulator shuttle; upon reaching of apredetermined rpm at a given setting of said throttle, said regulatorshuttle reciprocates without returning into said initial position ofrest.
 10. A method of prolonging the period of fuel injection into aninternal combustion engine during the idling rpm range by means of afuel injection pump of the type that includes a pump work chamber and atleast one reciprocating pump piston associated with said chamber,comprising the following steps: A. discharging in said rpm range througha bypass channel extending from said pump work chamber one part of thefuel displaced by said pump piston throughout its pressure strokes andB. closing said bypass channel by valve means when said engine operatesbeyond said rpm range.